U.S. patent number 7,256,474 [Application Number 10/777,189] was granted by the patent office on 2007-08-14 for semiconductor device having a guard ring.
This patent grant is currently assigned to Fujitsu Limited. Invention is credited to Mutsuaki Kai, Hiroyuki Kato, Masato Suga, Shigetoshi Wakayama.
United States Patent |
7,256,474 |
Wakayama , et al. |
August 14, 2007 |
Semiconductor device having a guard ring
Abstract
A multilayer interconnection structure of a semiconductor device
includes a first guard ring extending continuously along a
periphery of a substrate and a second guard ring extending
continuously in the multilayer interconnection structure along the
periphery so as to be encircled by the first guard ring and so as
to encircle an interconnection pattern inside the multilayer
interconnection structure, wherein the first and second guard rings
are connected with each other mechanically and continuously by a
bridging conductor pattern extending continuously in a band form
along a region including the first and second guard rings when
viewed in the direction perpendicular to the substrate.
Inventors: |
Wakayama; Shigetoshi (Kawasaki,
JP), Kai; Mutsuaki (Kawasaki, JP), Kato;
Hiroyuki (Kawasaki, JP), Suga; Masato (Kawasaki,
JP) |
Assignee: |
Fujitsu Limited (Kawasaki,
JP)
|
Family
ID: |
32985200 |
Appl.
No.: |
10/777,189 |
Filed: |
February 13, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040188843 A1 |
Sep 30, 2004 |
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Foreign Application Priority Data
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Mar 27, 2003 [JP] |
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2003-088139 |
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Current U.S.
Class: |
257/620; 257/758;
257/E23.002; 257/E23.145 |
Current CPC
Class: |
H01L
23/564 (20130101); H01L 23/585 (20130101); H01L
2924/0002 (20130101); H01L 2924/0002 (20130101); H01L
2924/00 (20130101) |
Current International
Class: |
H01L
23/544 (20060101) |
Field of
Search: |
;257/620,758,759,760,774,211,E23.145,E23.17,E23.18 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Pham; Hoai
Attorney, Agent or Firm: Westerman, Hattori, Daniels &
Adrian, LLP.
Claims
What is claimed is:
1. A semiconductor device, comprising: a semiconductor substrate;
and a multilayer interconnection structure formed on said
semiconductor substrate, said multilayer interconnection structure
comprising: a first guard ring extending continuously in said
multilayer interconnection structure along a periphery of said
semiconductor substrate; and a second guard ring extending
continuously in said multilayer interconnection structure along
said periphery so as to be encircled by said first guard ring, said
second guard ring encircling an interconnection pattern inside said
multilayer interconnection structure; said first and second guard
rings being connected with each other mechanically and continuously
by a bridging conductor pattern extending continuously in a band
form along a region including said first and second guard rings,
when viewed in the direction perpendicular to a principal surface
of said semiconductor substrate.
2. The semiconductor device as claimed in claim 1, wherein said
bridging conductor pattern does not have any of a gap or an
opening.
3. The semiconductor device as claimed in claim 1, wherein said
bridging conductor pattern is provided at plural different
positions having different heights as measured from a surface of
said semiconductor substrate.
4. The semiconductor device as claimed in claim 1, wherein said
bridging conductor pattern is formed in one or more interlayer
insulation films in said multilayer interconnection structure.
5. The semiconductor device as claimed in claim 1, wherein said
multilayer interconnection structure has a layered structure in
which a plurality of interlayer insulation films each including an
interconnection layer corresponding thereto are stacked, and
wherein an interconnection layer formed in one interlayer
insulation film of said plural interlayer insulation films is
connected to an underlying interconnection layer by a via-plug,
each of said first and second guard rings having a layered
structure identical to that of said multilayer interconnection
structure, said bridging conductor pattern being formed at a height
identical to that of the interconnection layer in said interlayer
insulation film in which said bridging conductor pattern is formed.
Description
CROSS-REFERENCE TO RELATED APPLICATION
The present application is based on Japanese priority application
No. 2003-088139 filed on Mar. 27, 2003, the entire contents of
which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The present invention generally relates to semiconductor devices
and more particularly to a semiconductor device having a multilayer
interconnection structure.
Conventionally, increase of operational speed has been attempted in
semiconductor devices by way of device miniaturization according to
the scaling law. On the other hand, in recent semiconductor
integrated circuits of high integration density, it is insufficient
to use a single interconnection layer for wiring semiconductor
devices of enormous numbers formed on the substrate, and thus, a
multilayer interconnection structure in which a number of
interconnection layers are stacked with intervening insulation
films is used generally for providing the necessary
interconnection.
In the semiconductor integrated circuit having such a multilayer
interconnection structure, on the other hand, it is practiced to
provide an anti-moisture guard ring (referred to hereinafter simply
as "guard ring") along a periphery of a chip so as to block
penetration of moisture or gas. Such a guard ring extends in the
multilayer interconnection structure continuously along the
periphery of the chip and interrupts the penetration path of
moisture or gas, which may be formed at the interface between an
interlayer insulation film and an interconnection layer.
FIGS. 1A and 1B show the construction of a semiconductor integrated
circuit 10 having such a conventional guard ring, wherein FIG. 1A
is a cross-sectional view of the foregoing semiconductor integrated
circuit 10 including a guard ring 1, while FIG. 1B is a plane view
showing the entirety of the chip of the semiconductor integrated
circuit 10.
Referring to FIG. 1A, the semiconductor integrated circuit 10 is
formed on a device region 11A defined on a Si substrate 11 by a
device isolation structure 11B and includes active devices such as
a MOS transistor formed on the device region 11A.
The semiconductor integrated circuit 10 includes a first multilayer
interconnection structure 12 formed on the substrate and includes
therein interconnection layers L1-L4 and via-plugs P1-P6 and a
second multilayer interconnection structure 13 formed on the first
multilayer interconnection structure 12, wherein the second
multilayer interconnection structure 13 includes therein
interconnection layers L5-L7 and via-plugs P7 and P8. In FIG. 1, it
should be noted that illustration of the interlayer insulation
films in the multilayer interconnection structures 12 and 13 is
omitted.
Further, as shown in the plan view of FIG. 1B, a guard ring 14 is
formed on the substrate 11 continuously along the periphery of the
chip.
Referring to FIG. 1A again, the guard ring 14 is formed by stacking
conductor patterns C1-C7 extending continuously along the periphery
of the chip respectively in correspondence to the interconnection
layers L1-L7 and conductor walls W1-W7 also extending continuously
along the periphery of the chip respectively in correspondence to
plugs P1a and P1b and also the plugs P2-P7.
Such a guard ring 14 has a layered structure corresponding to the
multilayer interconnection structures 12 and 13 and thus can be
formed at the time of formation of the multilayer interconnection
structure by a common process.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a semiconductor
device having a guard ring capable of blocking invasion of moisture
or gas into the semiconductor device from outside effectively and
with reliability.
Another object of the present invention is to provide a
semiconductor device having a guard ring occupying a small area and
yet capable of blocking invasion of moisture or gas into the
semiconductor device effectively and with reliability.
Another object of the present invention is to provide a
semiconductor device, comprising:
a substrate; and
a multilayer interconnection structure formed on said
substrate,
said multilayer interconnection structure comprising:
a first guard ring extending continuously in said multilayer
interconnection structure along a periphery of said substrate;
a second guard ring extending continuously in said multilayer
interconnection structure along said periphery so as to be
encircled by said first guard ring, said second guard ring
encircling an interconnection pattern inside said multilayer
interconnection structure;
said first and second guard rings being connected with each other
mechanically and continuously by a bridging conductor pattern
extending continuously in a band form along a region including said
first and second guard rings, when viewed in the direction
perpendicular to said substrate.
According to the present invention, the region between the first
and second guard rings is compartmented by the bridging conductor
pattern extending continuously along the band form region between
the first and second guard rings when viewed in the direction
perpendicular to the substrate. Thus, even in the case moisture or
gas has invaded to such a region, further penetration of the
moisture or gas to the interior of the semiconductor device is
blocked by the foregoing bridging conductor pattern. Thereby, the
bridging conductor pattern functions as a compartment wall or a
bulkhead. Thus, according to the present invention, by using the
two guard rings, invasion of moisture or gas is blocked positively
while suppressing the increase of area of the substrate surface
occupied by the guard ring.
Another object of the present invention is to provide a
semiconductor device, comprising:
a substrate;
a first multilayer interconnection structure formed on said
substrate;
a second multilayer interconnection structure formed on said first
multilayer interconnection structure,
said first multilayer interconnection structure comprising: a first
guard ring extending continuously in said first multilayer
interconnection structure along a periphery of said substrate; and
a second guard ring extending continuously in said first multilayer
interconnection structure along said periphery so as to be
encircled by said first guard ring, said second guard ring
encircling an interconnection pattern inside said first multilayer
interconnection structure,
said second multilayer interconnection structure comprising: a
bridging conductor pattern extending in said second multilayer
interconnection structure over a band form region continuously,
said bridging conductor pattern mechanically connecting said first
and second guard rings with each other; and a third guard ring
formed on said bridging conductor pattern.
According to the present invention, the area of the substrate
occupied by the first and second guard rings is minimized by
connecting the first and second guard rings formed in the first
multilayer interconnection structure to the third guard ring formed
in the second multilayer interconnection structure by way of the
bridging conductor pattern.
In the semiconductor device of the present invention, a very minute
interconnection pattern is formed in the first multilayer
interconnection structure of the lower layer by using a stringent
design rule, and associated with this, the first and second guard
rings are formed by a minute pattern with minute pitch or minute
interval. Contrary to this, the design rule is less stringent in
the second multilayer interconnection structure of the upper layer
where a large via-diameter is used. Thereby, the third guard ring
is formed by a wide conductor wall having a comparatively large
width in correspondence to the via-diameter. In the present
invention, the area of the substrate surface occupied by the guard
ring is minimized by providing the first and second guard rings
right underneath the third guard ring. Of course, the reliability
of the guard ring, and thus the reliability of the semiconductor
device, can be improved furthermore by forming a different bridging
conductor pattern in the first multilayer interconnection structure
so as to bridge the first and second guard rings.
Other objects and further features of the present invention will
become apparent from the following detailed description when read
in conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are diagrams showing the construction of a
semiconductor integrated circuit having a conventional multilayer
interconnection structure and a guard ring;
FIG. 2 is a diagram showing the construction of a semiconductor
integrated circuit having a dual guard ring structure and further
the problems caused in such a semiconductor integrated circuit;
FIG. 3 is a diagram showing the construction of a semiconductor
integrated circuit according to a first embodiment of the present
invention;
FIG. 4 is a plan view showing a part of FIG. 3 with an enlarged
scale;
FIG. 5 is a diagram explaining the function of the guard ring in
the semiconductor integrated circuit of FIG. 3;
FIG. 6 is another diagram explaining the function of the guard ring
in the semiconductor integrated circuit of FIG. 3;
FIGS. 7A-7C are diagrams explaining the fabrication process of the
guard ring used in the semiconductor integrated circuit of FIG.
3;
FIG. 8 is a diagram showing a modification of the semiconductor
integrated circuit of FIG. 3;
FIG. 9 is a diagram showing the construction of a semiconductor
integrated circuit according to a second embodiment of the present
invention; and
FIG. 10 is a diagram showing a modification of the semiconductor
integrated circuit of FIG. 9.
DETAILED DESCRIPTION OF THE INVENTION
In recent ultrafine semiconductor integrated circuits, low
dielectric constant films called low-K film having a low specific
dielectric constant is used as the interlayer insulation film for
suppressing the problem of parasitic capacitance of wiring. It
should be noted that parasitic capacitance of wiring becomes
conspicuous with the progress of device miniaturization and becomes
a serious problem in high-density integrated circuits. Such a low
dielectric constant film includes those films having a specific
dielectric constant of 2.0-3.0 or less, such as an aromatic
hydrocarbon polymer film marketed under the trademark of SiLK or
Flare, or a porous film thereof. Such a low dielectric constant
film is used predominantly for the lower multilayer interconnection
structure 12 located near the substrate 11, in which
interconnection patterns are formed with minimum separation.
Such a low dielectric constant film generally has the feature of
low density in correspondence to the feature of low specific
dielectric constant, and because of this, various investigations
and proposals have been made for a multilayer interconnection
structure that uses a low dielectric constant interlayer insulation
film in relation to securing adhesion between the interconnection
pattern and the interlayer insulation film.
The similar situation applies also to the case of the guard ring
14, and thus, there can be a case in which gap is formed between
any of the conductor patterns C1-C7 such as the conductor pattern
C3 and the conductor wall formed adjacent thereto.
When a gap is formed in the guard ring, such a part can serve for
the path of moisture or external gas into the multilayer
interconnection structure. As shown in FIG. 1A, moisture or gas
thus invaded can cause various problems such as defective contact,
increase of resistance, disconnection of interconnection pattern,
and the like, when it has caused diffusion into the multilayer
interconnection structures 12 and 13. Further, in the case the
moisture or gas thus invaded has reached the active device such as
a MOS transistor formed on the surface of the substrate 11, there
is a possibility that the active device may experience
degradation.
In order to solve such problems, it has been practiced to provide a
guard ring of double structure by using guard rings 14A and 14B as
shown in FIG. 2, wherein those parts of FIG. 2 explained previously
are designated by the same reference numerals and the description
thereof will be omitted. In the illustrated example, the guard
rings 14A and 14B have the same construction as the guard ring 14
of FIG. 1.
By using such a guard ring of double structure, the probability of
invasion of moisture or gas into the multilayer interconnection
structures 12 and 13 is reduced significantly.
In the construction of FIG. 2, however, the moisture or the gas
invaded inside the guard ring 14A can cause diffusion in the
stacked structure between the guard rings 14A and 14B in the case
there is formed a defect somewhere in the outer guard ring 14A
extending continuously along the chip periphery and in the case
there is formed a defect somewhere in the inner guard ring 14B
extending continuously along the chip periphery as shown in FIG. 2.
Ultimately, the moisture or gas can enter the region inside the
guard ring 14B.
Thus, there are cases in which the semiconductor integrated circuit
having the guard ring of the double structure of FIG. 2 cannot
satisfy the reliability and lifetime specified for the
semiconductor integrated circuit.
Further, in the case of the semiconductor integrated circuit having
the guard ring of the double structure of FIG. 2, the guard ring
occupies substantial area of the substrate 11, and because of this,
there arises the problem in that the area for forming the active
device or the multilayer interconnection structure is
decreased.
As explained previously, very minute interconnection patterns
having the via-diameter of 0.9 .mu.m or less, for example, are
formed with close separation and thus with high density in the
lower multilayer interconnection structure 12, by using a low
dielectric interlayer insulation film. On the other hand, in the
upper multilayer interconnection structure 13, the design rule for
the interconnection pattern is less stringent, and thus, there are
cases in which a via-diameter of about 1.7 .mu.m is used.
In such a structure, the separation between the guard rings 14A and
14B is determined substantially by the via-diameter in the
multilayer interconnection structure 13, and there appears a waste
region in the multilayer interconnection structure 12 between the
guard rings 14A and 14B in which formation of a functional element
of the semiconductor device is not possible.
Further, it should be noted that an interlayer insulation film of
low dielectric constant is generally a low density film as
explained previously, and because of this, the low dielectric film
generally shows poor mechanical performance such as poor Young
modulus. Because of this, there is a tendency in the guard ring 14
of FIG. 1 that concentration of stress occurs in the conductor
patterns C1-C4 or in the conductor walls W1-W5 corresponding to the
lower multilayer interconnection structure 12 when an external
stress is applied. Thereby, the conductor patterns C1-C4 or the
conductor walls W1-W5 may easily undergo deformation. When
deformation is caused in any of the conductor patterns C1-C4 or in
the conductor walls W1-W5, there is formed an invasion path of
moisture or external gas as explained previously.
FIRST EMBODIMENT
FIG. 3 shows the construction of a semiconductor integrated circuit
20 according to a first embodiment of the present invention.
Referring to FIG. 3, the semiconductor integrated circuit 20 is
formed on a Si substrate 21 having a device region 21A defined by a
device isolation structure 21B, and a MOS transistor including a
gate electrode 22G and diffusion regions 21a and 21b is formed in
the device region 21A such that the diffusion regions 21a and 21b
are formed in the Si substrate 21 at both lateral sides of the gate
electrode 22G. In FIG. 3, it should be noted that illustration of
the gate insulation film is omitted. Further, similarly to a usual
MOS transistor, the gate electrode 22G is provided with a pair of
sidewall insulation films of SiO.sub.2 or SiON.
The gate electrode 22G is covered by an interlayer insulation film
22 formed on the substrate 21, wherein the interlayer insulation
film 22 forms a part of the first multilayer interconnection
structure 31 formed on the substrate 21.
Thus, on the interlayer insulation film 22, interlayer insulation
films 23-26 are formed consecutively, and an interconnection
pattern 22W and via-plugs 22P.sub.1, and 22P.sub.2 are formed in
the interlayer insulation film 22 so as to fill the wiring groove
or via-holes formed in the film 22 by way of a dual damascene
process, by filling the wiring grooves or via-holes by a conductor
layer and by removing the unnecessary conductor layer on the
interlayer insulation film 22 by a CMP (chemical mechanical
polishing) process. As a result of the dual damascene process, the
interconnection pattern 22W has a principal surface coincident to
the surface of the interlayer insulation film 22. Further, in the
illustrated example, the via-plugs 22P.sub.1, and 22P.sub.2 make a
contact to the diffusion regions 21a and 21b, respectively.
A similar interconnection structure is formed in each of the
interlayer insulation films 23-26. Thus, in the interlayer
insulation film 23, there are formed an interconnection layer 23W
and a via-plug 23P, while an interconnection layer 24W and a
via-plug 24P are formed in the interlayer insulation film 24.
Further, an interconnection layer 25W and a via-plug 25P are formed
in the interlayer insulation film 25 and a via-plug 26P is formed
in the interlayer insulation film 26.
Typically, the interlayer insulation films 23-26 are formed of an
organic polymer film having a specific dielectric constant of less
than 3.0, while the interconnection layers 22W-25W and the
via-plugs 22P.sub.1, and 22P.sub.2 and 23P-26P are formed of Cu.
Further, the interconnection layers 22W-25W and the via-plugs
22P.sub.1, and 22P.sub.2 and 23P-26P can be formed also by using Al
or an Al alloy or other conductors.
On the interlayer insulation film 26, there is formed an
interconnection layer 27W typically formed of Al or an Al alloy so
as to make a contact with the via-plug 26P, wherein the
interconnection layer 27W forms a part of another multilayer
interconnection structure 32 formed on the multilayer
interconnection structure 31.
Thus, the interconnection layer 27W is covered with an interlayer
insulation film 27 and a next interconnection layer 28W is formed
on the interlayer insulation film 27. The interconnection layer
28W, in turn, is connected to the interlayer insulation film 27
through a via-plug 27P formed in the interconnection layer 27W.
Similarly, the interconnection layer 28W is covered with an
interlayer insulation film 28 formed on the interlayer insulation
film 27, and a next interconnection layer 29W is formed on the
interlayer insulation film 28. The interconnection layer 29W is
connected to the interconnection layer 28W through a via-plug 28P
formed in the interlayer insulation film 28.
In a typical example, the interlayer insulation films 27 and 28 are
formed of SiOC or SiO.sub.2 while the interconnection layers
27W-29W are formed of Al or an Al alloy. Further, the via-plugs 27P
and 28P are formed by W (tungsten), and the like.
Furthermore, a passivation film 29 of SiN, and the like, is formed
on the interlayer insulation film 28.
In the semiconductor integrated circuit 20 of FIG. 3, an outer
guard ring 33A and an inner guard ring 33B are formed so as to
extend continuously along the periphery of the substrate such that
the interconnection layers in the multilayer interconnection
structures 31 and 32 are encircled. Reference should be made to the
plan view of FIG. 1B.
Referring to FIG. 3, the guard ring 33A includes: a conductor wall
22PA formed in the interlayer insulation film 22 simultaneously to
the via-plugs 22P.sub.1, and 22P.sub.2 by the same material thereto
so as to extend in the interlayer insulation film 22 continuously
along a periphery of the substrate 21 without forming a gap with a
width substantially the same as the diameter of the via-plugs; and
a conductor pattern 22WA formed in the interlayer insulation film
22 simultaneously to the interconnection layer 22W by the same
material thereto so as to extend on the conductor wall 22PA
continuously along the periphery of the substrate without forming a
gap. Further, in the interlayer insulation film 23, there are
formed, as a part of the guard ring 33A, a conductor wall 23PA
extending on the conductor pattern 22WA continuously along the
periphery of the substrate 21 without forming a gap with a width
substantially the same as the diameter of the via-plug 23P, and a
conductor pattern 23WA extending on the conductor wall 23PA along
the substrate periphery continuously without forming a gap, wherein
the conductor wall 23PA is formed simultaneously to the via-plug
23P by the same material, while the conductor pattern 23WA is
formed in the interlayer insulation film 23 simultaneously to the
interconnection layer 23W by the same material.
Further, the guard ring 33A includes: a conductor wall 24PA formed
in the interlayer insulation film 24 simultaneously to the via-plug
24P by the same material thereto so as to extend on the conductor
pattern 23WA continuously along the periphery of the substrate 21
with substantially the same width as the diameter of the via-plug
24P without forming a gap; a conductor pattern 24WA formed in the
interlayer insulation film 24 simultaneously to the interconnection
layer 24W by the same material so as to extend on the conductor
wall 24PA continuously along the substrate periphery without
forming a gap; a conductor pattern 25WA formed in the interlayer
insulation film 25 simultaneously to the interconnection layer 25W
by the same material thereto so as to extend on the conductor wall
24PA continuously along the periphery of the substrate without
forming a gap; and a conductor wall 25PA formed in the interlayer
insulation film 25 simultaneously to the via-plug 25P by the same
material thereto so as to extend on the conductor pattern 24WA with
a width the substantially the same width as the via-diameter of the
via-plug 25P continuously along the periphery of the substrate 21
without forming a gap.
In the interlayer insulation film 25, there is formed a conductor
pattern 25WA formed simultaneously to the interconnection layer 25W
by the same material such that the conductor pattern 25WA extends
on the conductor wall 25PA continuously without forming a gap.
Further, the guard ring 33A includes a conductor wall 26PA formed
simultaneously to the via-plug 26P by the same material thereto so
as to extend continuously in the interlayer insulation film 26 on
the conductor pattern 25WA with substantially the same width as the
diameter of the via-plug 26P along the periphery of the substrate
21 without forming a gap. The guard ring 33A further includes, on
the conductor wall 26PA, a conductor pattern 27WA formed in the
interlayer insulation film 27 simultaneously to the interconnection
layer 27W by the same material thereto so as to extend on the
conductor wall 26PA along the substrate periphery continuously
without forming a gap, and a conductor wall 27PA formed
simultaneously to the via-plug 27P by the same material thereto so
as to extend on the conductor pattern 27WA along the periphery of
the substrate circumference continuously without forming a gap.
Further, the guard ring 33A includes: a conductor pattern 28WA
formed on the conductor wall 27PA in the interlayer insulation film
27 simultaneously to the interconnection layer 28W by the same
material thereto so as to extend on the conductor wall 26PA
continuously along the periphery of the substrate without forming a
gap; and a conductor wall 28PA formed simultaneously to the
via-plug 28P by the same material thereto so as to extend on the
above-mentioned conductor pattern 28WA continuously along the
periphery of the substrate without forming a gap. Further, in the
passivation film 29, there is formed a conductor pattern 29WA on
the conductor wall 28PA simultaneously to the interconnection layer
29W by the same material as a part of the guard ring 33A.
Similarly, the guard ring 33B includes: a conductor wall 22PB
formed in the interlayer insulation film 22 simultaneously to the
conductor wall 22PA by the same material thereto so as to extend in
the interlayer insulation film 22 continuously along the periphery
of the substrate 21 with a width substantially the same as the
via-diameter of the via-plug 22P.sub.1, or 22P.sub.2 without
forming a gap; and a conductor pattern 22WB formed in the
interlayer insulation film 22 simultaneously to the conductor
pattern 22WA by the same material thereto so as to extend on the
conductor wall 22PB continuously along the periphery of the
substrate without forming a gap. Further, in the above-mentioned
interlayer insulation film 23, there are provided, as a part of the
guard ring 33B, a conductor wall 23PB formed simultaneously to the
conductor wall 23PA by the same material thereto so as to extend on
the conductor pattern 22WB continuously along the periphery of the
substrate 21 with a width substantially the same as the diameter of
the via-plug 23P without forming a gap, and a conductor pattern
23WB formed in the interlayer insulation film 23 simultaneously to
the conductor pattern 23WA by the same material so as to extend on
the conductor wall 23PB along the periphery of the substrate
continuously without forming a gap.
Further, the guard ring 33B includes: a conductor wall 24PB formed
in the interlayer insulation film 24 simultaneously to the
conductor wall 24PA by the same material thereto so as to extend on
the conductor pattern 23WB along the periphery of the substrate 21
continuously with a width substantially the same as the diameter of
the via-plug 24P without forming a gap; and a conductor pattern
24WB formed in the interlayer insulation film 24 simultaneously to
the conductor pattern 24WA by the same material thereto so as to
extend on the conductor wall 24PB top along the periphery of the
substrate continuously without forming a gap. Further, the guard
ring 33B includes a conductor pattern 25WB formed in the interlayer
insulation film 25 simultaneously to the conductor pattern 25WA
with the same material thereto so as to extend on the conductor
wall 24PB continuously along the periphery of the substrate without
forming a gap, and a conductor wall 25PB formed in the interlayer
insulation film 25 simultaneously to the conductor wall 25PA by the
same material thereto so as to extend on the conductor pattern 24WB
along the periphery of the substrate 21 with a width substantially
the same as the diameter of the via-plug 25P continuously without
forming a gap.
In the interlayer insulation film 25, there further extends a
conductor pattern 25WB formed simultaneously to the conductor
pattern 25WA by the same material thereto on the conductor wall
25PB continuously without forming a gap.
Further, the guard ring 33B includes a conductor wall 26PB formed
simultaneously to the conductor wall 26PA by the same material
thereto in the interlayer insulation film 26 so as to extend on the
conductor pattern 25WB along the periphery of the substrate 21
continuously a width the same as the diameter of the via-plug 26P
without forming a gap. Further, the guard ring 33B includes a
conductor pattern 27WB formed on the conductor wall 26PB in the
interlayer insulation film 27 simultaneously to the conductor
pattern 27WA by the same material thereto so as to extend on the
conductor wall 26PB along the periphery of the substrate
continuously without forming a gap, and a conductor pattern 27PB
formed simultaneously to the conductor wall 27PA by the same
material thereto so as to extend on the conductor pattern 27WB
continuously along the periphery of the substrate without forming a
gap.
Furthermore, the guard ring 33B includes: a conductor pattern 28WB
formed on the conductor wall 26PB in the interlayer insulation film
27 simultaneously to the conductor pattern 28WA by the same
material thereto so as to extend on the conductor wall 27PB
continuously along the periphery of the substrate without forming a
gap; and a conductor wall 28PB formed simultaneously to the
conductor wall 28PA by the same material thereto so as to extend on
the conductor pattern 28WB along the periphery of the substrate
continuously without forming a gap. Further, in the passivation
film 29, there is formed a conductor pattern 29WB on the conductor
wall 28PB as a part of the guard ring 33B, simultaneously to the
interconnection layer 29W by the same material thereto.
Thereby, as can be seen in FIG. 3, the conductor pattern 23WA and
the conductor pattern 23WB are connected, and there is formed a
conductor pattern 23WC extending continuously along the periphery
of the substrate 11 as shown in FIG. 4. Similarly, the conductor
pattern 27WA and the conductor 27WB are connected, and there is
formed a conductor pattern 27WC extending continuously along the
periphery of the substrate 11 similarly to FIG. 4. Thus, the
conductor pattern 23WC and the conductor pattern 27C thus formed
bridges across the guard ring 33A and the guard ring 33B.
As can be seen in FIG. 4, the conductor pattern 23WC extends
continuously without forming a gap, and thus, there is formed no
opening, and the like. Further, as shown in FIG. 4 by a dotted
line, the upper and lower conductor walls 23PA and 23PB of the
conductor pattern 23WC extend continuously along the periphery of
the substrate 21 without forming a gap.
In the construction of FIG. 3, it should be noted that, even in the
case there is formed a defect x in a part of the guard ring 33A and
also in the guard ring 33B as shown in FIG. 5, moisture or gas
invaded from outside is blocked by the bridging conductor pattern
23 C as long as the defect is formed in the region isolated by the
bridging conductor pattern 23C and cannot invade further into the
region inside the guard ring 33B. In other words, the bridging
conductor pattern 23C or 27C of the present embodiment functions as
a bulkhead or compartment wall compartmenting the region between
guard ring 33A and the guard ring 33B into plural compartments.
Further, as shown in FIG. 6 the path of the external moisture or
gas invading into the region inside the guard ring 33B can be
blocked by using the conductor pattern 23C even in the case there
exists a defect x in each of the guard rings 33A and 33B as long as
the defects are formed in the different regions isolated by the
bridging conductor pattern 23C. Thus, the reliability of the
semiconductor device can be improved significantly. Contrary to
this, in the case the guard ring has the structure of FIG. 2, the
invasion path cannot be blocked and external moisture or gas can
penetrate easily to the interior of the semiconductor integrated
circuit.
FIGS. 7A-7C show a part of the process of forming the guard rings
33A and 33B of FIG. 3.
Referring to FIG. 7A, the interlayer insulation film 22 is formed
with the interconnection layer 22W, and the conductor pattern 22WA
and the conductor wall 22PA are formed further in correspondence to
the guard ring 33A. Further, the conductor wall 22PB and the
conductor pattern 22WB are formed in correspondence to the guard
ring 33B. The next interlayer insulation film 23 is then formed on
the interlayer insulation film 22. Next, the conductor pattern 23A
and the via-plug 23P are formed in the interlayer insulation film
23 respectively for the wiring groove 23G and for the via-hole 23H.
Simultaneously to this, a groove 23g for the bridging conductor
pattern 23C and the grooves 23a and 23b for the conductor walls
23PA and 23PB are formed in the interlayer insulation film 23 in
correspondence to the guard rings 33A and 33B.
Next, in the step of FIG. 7B, the surface of the interlayer
insulation film 23 of FIG. 7A, including the wiring groove 23G, the
via-hole 23H and the grooves 23a, 23b and, 23g, it covered with a
barrier metal film such as TaN (not illustrated), and thereafter,
the groove 23G, the via-hole 23H and the grooves 23a, 23b, 23g are
filled with a conductor layer 23Cu such as Cu or W.
Further, in the step of FIG. 7C, unnecessary conductor layer 23Cu
on the surface of the interlayer insulation film 23 is removed by a
CMP (chemical mechanical polishing) process, and a structure in
which the wiring groove 23G and the via-hole 23H are filled with
the conductor layer 23W and the via-plug 23P respectively and the
grooves 23a, 23b and 23g are filled with the conductor walls 23PA
and 23PB and the conductor pattern 23WC respectively, is
obtained.
By repeating such a process, it becomes possible to form the guard
rings 33A and 33B without inviting increase of number of the
process steps.
In the construction of FIGS. 7A-7C, it should be noted that the
conductor walls 22PA-28PA or the conductor wall 22PB-28PB are
formed in alignment in the direction perpendicular to the substrate
11. However, this is not a necessarily condition, and it is also
possible to displace the position thereof within the extent of the
conductor patterns 23WA-29WA as shown in the modification of FIG.
8. Further, the conductor walls 22PA-28PA or the conductor walls
22PB-28PB can be formed also in a zigzag form inside the extent of
the conductor pattern 22WA-29WA or the conductor pattern 22WB-29WB,
which extend in the band-like form along the substrate periphery
when viewed in the direction perpendicular to the principal surface
the substrate 11.
In the present embodiment, it should be noted that the interlayer
insulation films 22-28 are not limited to the aromatic hydrocarbon
polymer film such as SiLK and FLARE, but it is also possible to use
various low dielectric constant films such as an MSQ (methyl
silsesquioxane) film or a HOSP (hydrido-organic siloxane polymer)
film, or a porous film thereof, for the interlayer insulation films
22-28.
Further, the interconnection layers 22W-25W and the via-plugs
22P-26P, and thus, the conductor patterns 22WA-25WA and 22WB-25WB,
and further the conductor walls 22PA-26PA and 22PB-26PB, are not
limited to Cu or W, but it is also possible to use Al or an Al
alloy in place thereof.
SECOND EMBODIMENT
FIG. 9 shows the construction of a semiconductor device 40
according to a second embodiment of the present invention, wherein
those parts corresponding to the parts explained previously are
designated by the same reference numerals and description thereof
will be omitted.
Referring to FIG. 9, the interval between the guard ring 33A and
the guard ring 33B on the substrate 21 is reduced in the present
embodiment, and associated with this, there is formed, on the
conductor pattern 27WC, a single guard ring 33C in the form of
stacking of: a single conductor wall 27PC corresponding to the
conductor plug 27P; a single conductor pattern 28WC corresponding
to the interconnection layer 28W; a single conductor wall 28PC
corresponding to the conductor plug 28P; and a single conductor
pattern 29WC corresponding to the interconnection layer 29W.
As shown in FIG. 9, in the semiconductor device of the construction
in which the multilayer interconnection structure 32 including
therein an interconnection layer of Al or an Al alloy is provided
on a high integration density multilayer interconnection structure
31 that uses a low dielectric constant interlayer insulation film
by using an usual interlayer insulation film of SiOC or SiO.sub.2,
it should be noted that the interval between the guard rings 33A
and 33B in the multilayer interconnection structure 31 of high
integration density can be reduced by applying a stringent design
rule of 0.9 .mu.m or less thereto.
With this, the area of the substrate surface occupied by the guard
rings 33A and 33B is decreased in the multilayer interconnection
structure 31, and the region usable for formation of the active
devices and interconnection patterns is increased. Particularly,
because the guard ring is formed along the periphery of the
substrate or chip, a small decrease of interval of the guard rings
33A and 33B can provide a substantial effect for increasing the
substrate area usable for formation of active elements or
interconnection patterns.
Meanwhile, in the structure of FIG. 9, a more relaxed design rule
is used in the multilayer interconnection structure 32 of the upper
layer, and because of this, there is no decrease in the diameter of
the via-plug 27P or 28P, and hence the width of the conductor wall
27PC or 28PC. Thus, as shown in FIG. 9, it becomes possible to form
the guard ring 33A and 33B in the multilayer interconnection
structure 31 so as to locate right underneath the guard ring 33C
formed in the multilayer interconnection structure 32.
In such a structure, the guard ring 33C is supported by the guard
rings 33A and 33B, and because of this, the stress applied to the
guard ring 33C is shared by the guard rings 33A and 33B, and thus,
the stress applied to each of the guard rings 33A and 33B formed in
the interlayer insulation films 22-26 of low Young modulus is
reduced. Associated with this, the occurrence of defects in the
guard rings 33A and 33B. explained with reference to FIG. 5 is
suppressed, and the reliability of the semiconductor device is
improved.
FIG. 10 shows an example in which the interval between the guard
ring 33A and the guard ring 33B is reduced in the semiconductor
device 40 of FIG. 9 such that the interval between the conductor
wall 22PA and the conductor wall 22PB is narrowed to the degree
corresponding to the via-diameter.
Referring to FIG. 10, it should be noted that the guard ring is
formed so as to bridge the conductor pattern in each the interlayer
insulation films 22-25 in this case, and thus, the bridging
conductor pattern 22WC bridges the conductor walls 22PA and 22PB in
the interlayer insulation film 22. Similarly, the bridging
conductor pattern 23WC bridges the conductor walls 23PA and 23PB in
the interlayer insulation film 23, the bridging conductor pattern
24WC bridges the conductor walls 24PA and 24PB in the insulation
film 24, and the bridging conductor pattern 25WC bridges the
conductor walls 25PA and 25PB in the interlayer insulation film
25.
According to the construction of FIG. 10, the area occupied by the
multiple guard ring structure in the high density multilayer
interconnection structure formed above the substrate surface and
also immediately on the substrate surface is minimized, and it
becomes possible to form larger number of active devices or wiring
structures on the substrate.
In the present embodiment, too, the interlayer insulation films
22-28 is not limited to the aromatic hydrocarbon polymer film such
as SiLK or FLARE, similarly to the previous embodiment, and it is
possible to use, for the interlayer insulation films 22-28, various
low dielectric constant films such as an organo-siloxane film
including an MSQ (methyl silsesquioxane) film, a HOSP
(hydrido-organic siloxane polymer) film, and the like, or a porous
film thereof.
Further, the interconnection layers 22W-25W, the via-plugs 22P-26P,
and hence the conductor patterns 22WA-25WA, 22WB-25WB, and also the
conductor walls 22PA-26PA and 22PB-26PB, are not limited to Cu and
W, but it is also possible to use Al or an Al alloy in place
thereof.
Further, the present invention is not limited to the embodiments
described heretofore, but various variations and modifications may
be made without departing from the scope of the invention.
* * * * *